build method

@override Future<void> build(BuildStep buildStep)

Generates the outputs for a given BuildStep.

Implementation

@override
Future<void> build(BuildStep buildStep) async {
  await _buildPool.withResource(() async {
    var dartEntrypointId = buildStep.inputId;
    var isAppEntrypoint = await _isAppEntryPoint(dartEntrypointId, buildStep);
    if (!isAppEntrypoint) return;

    var moduleId =
        buildStep.inputId.changeExtension(moduleExtension(vmPlatform));
    var module = Module.fromJson(
        json.decode(await buildStep.readAsString(moduleId))
            as Map<String, dynamic>);

    List<Module> transitiveModules;
    try {
      transitiveModules = await module
          .computeTransitiveDependencies(buildStep, throwIfUnsupported: true);
    } on UnsupportedModules catch (e) {
      var librariesString = (await e.exactLibraries(buildStep).toList())
          .map((lib) => AssetId(lib.id.package,
              lib.id.path.replaceFirst(moduleLibraryExtension, '.dart')))
          .join('\n');
      log.warning('''
Skipping compiling ${buildStep.inputId} for the vm because some of its
transitive libraries have sdk dependencies that not supported on this platform:

$librariesString

https://github.com/dart-lang/build/blob/master/docs/faq.md#how-can-i-resolve-skipped-compiling-warnings
''');
      return;
    }

    var transitiveKernelModules = [
      module.primarySource.changeExtension(vmKernelModuleExtension),
      for (var module in transitiveModules.reversed)
        module.primarySource.changeExtension(vmKernelModuleExtension),
    ];
    var appContents = [
      for (var dependencyId in transitiveKernelModules)
        ...await buildStep.readAsBytes(dependencyId)
    ];
    await buildStep.writeAsBytes(
        buildStep.inputId.changeExtension(vmKernelEntrypointExtension),
        appContents);
  });
}